1. Field of the Invention
The present invention relates to polyethylene articles, and more particularly to high-gloss polyethylene articles having excellent properties.
2. Background of the Art
The number of consumer products or packaging for consumer products that contain polymers continues to increase everyday. As such, there is a growing need to develop polymers that can be used to form more appealing products for consumers. Industry is concerned with forming end use polymer articles that exhibit a high level of gloss because consumers find the glossy appearance of certain products desirable. For example, it is believed that consumers are more likely to buy a product contained within a glossy plastic bottle because they correlate the glossy bottle with a higher quality product.
Technically speaking, gloss is defined as the ratio of the reflected light from a material to the scattered light at a specific angle of incidence, multiplied by 100 to yield a percentage (“%” is herein understood to mean percent). According to ASTM D2457, specular gloss is the ratio of the flux reflected in specular direction to incident flux for a specified angle of incidence and source and receptor angular apertures. Polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) formed according to conventional polymerization methods and fabricated into end use articles by equipment known in the art are considered to exhibit relatively high levels of gloss. Thus, PP, PET, and PVC are well suited for forming end use articles, such as health and beauty product bottles, for which a glossy appearance is desired.
In contrast, polyethylene (PE) produced according to conventional polymerization processes, e.g., using a chromium or Ziegler-Natta catalyst, typically does not achieve a sufficient level of gloss for use in such products. PE can have advantages over PP, PET and PVC due to one or more of the following attributes: recycle ability, toughness, chemical resistance, barrier properties, adaptability to various fabrication techniques and the ability to fine tune physical properties. Furthermore, polyethylene can be processed using common methods, e.g., blow molding or extrusion, whereas PET must be processed using stretchable molding, which requires special equipment. PVC has the additional drawback of environmental concerns.
Therefore, a need exists for PE articles having equivalent or higher gloss levels than those of the gloss levels of PP, PET, and PVC articles. The PE articles of the present invention meet this need because they have several desirable physical and processing properties, including relatively high levels of gloss.